﻿<p>The IfcSurfaceOfRevolution</em> is a surface derived by rotating a curve about an axis.
</p>
<blockquote class="extDef">
NOTE&nbsp; Definition according to ISO/CD 10303-42:1992<br>
A surface of revolution is the surface obtained by rotating a curve one complete revolution about an axis. The data shall be interpreted as below.<br><br>
	 
The parameterization is as follows where the curve has a parameterization &lambda;(<em>u</em>):

<blockquote>
<p style="font-size:inherit"><b>C</b> = AxisPosition.Location<BR><B>V</B> = AxisPosition.Z</p>
<img src="../../../figures/ifcsurfaceofresolution-math1.gif" width="494" height="22">
</blockquote>

In order to produce a single-valued surface with a complete revolution, the curve shall be such that when expressed in a cylindrical coordinate system (<em>r,&phi; ,z</em>) centred at <b>C</b> with an axis <b>V</b>, no two distinct parametric points on the curve shall have the same values for (<em>r, z</em>). For a surface of revolution the parametric range is 0 &lt; <em>u</em> &lt; 360 degree. The parameterization range for <em>v</em> is defined by referenced curve.</blockquote> 

<blockquote class="note">NOTE&nbsp; Entity adapted from <strong>surface_of_revolution</strong> defined in ISO
10303-42.</blockquote>

<blockquote class="history">
HISTORY&nbsp; New entity in IFC2x.
</blockquote> 

<p class="spec-head">Informal Propositions:</p> 
<ol> 
<li>The surface shall not self-intersect</li> 
<li>The swept curve shall not be coincident with the axis line for any finite part of its legth.</li> 
</ol>